Engine swap problem

A big problem i've noticed when i've seen many different youtube videos is the unchanging rev counter when a different engine is put into a car. This is really noticeable with rotary engines which should be revving up to at least 10,000 rpm and not the same rpm as a normal v6 engine. I know it's something pretty simple, but it's just annoying to see an unchanging rpm counter when these engine changes are seeming like they are going to be a big part of the game.